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We measured the transmission and reflection spectra of a chaotic microwave billiard in the regime of isolated and overlapping resonances. By inserting a ferrite inside the cavity violation of time-reversal (T) invariance was induced. Only partial T-invariance violation is achievable. For the random-matrix theoretical description of fluctuation properties of the complex scattering matrix elements extracted from the measured spectra a scattering approach originally developed in the context of compound nucleus reactions is used. Based on this scattering formalism and the supersymmetry method we derived analytic expressions for the autocorrelation function and the cross-correlation coefficient of pairs of complex conjugate scattering matrix elements. These are applicable in the regime of isolated and of overlapping resonances and depend on a parameter, which defines the strength of the T-invariance violation. Fitting the measured scattering data we determined the parameters of this model, the transmission coefficients and the strength of T-invariance violation, for the whole range of the excitation frequency. Furthermore, the elastic enhancement factor was determined and distributions of the scattering matrix elements were investigated for different excitation frequencies. Using the fitted parameters, a comparison with the corresponding theoretical predictions provides a stringent test of the model. This work was supported by the DFG within the SFB634 |
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